    function LimitTextArea(field){ 
       maxlimit=100; 
       if (field.value.length > maxlimit) 
        field.value = field.value.substring(0, maxlimit);
     }
    $.weui = {};  
    $.weui.alert = function(options){  
      options = $.extend({title: '警告', text: '警告内容'}, options);  
      var $alert = $('.weui_dialog_alert');  
      $alert.find('.weui_dialog_title').text(options.title);  
      $alert.find('.weui_dialog_bd').text(options.text);  
      $alert.on('touchend click', '.weui_btn_dialog', function(){  
        $alert.hide();  
      });  
      $alert.show();  
    };  
    $(function(){
        // 允许上传的图片类型  
        var allowTypes = ['image/jpg', 'image/jpeg', 'image/png'];  
        // 1024KB，也就是 1MB  
        var maxSize = 1024 * 1024;  
        // 图片最大宽度  
        var maxWidth = 500;  
        // 最大上传图片数量  
        var maxCount = 3;  
        $('.js_file').on('change', function (event) {  
          var files = event.target.files;  
          
            // 如果没有选中文件，直接返回  
            if (files.length === 0) {  
              return;  
            }  
            
            for (var i = 0, len = files.length; i < len; i++) {  
              var file = files[i];  
              var reader = new FileReader();  
              
                // 如果类型不在允许的类型范围内  
                if (allowTypes.indexOf(file.type) === -1) {  
                  $.weui.alert({text: '该类型不允许上传'});  
                  continue;  
                }  
                
                if (file.size > maxSize) {  
                  $.weui.alert({text: '图片太大，不允许上传'});  
                  continue;  
                }  
                
                if ($('.weui_uploader_file').length >= maxCount) {  
                  $.weui.alert({text: '最多只能上传' + maxCount + '张图片'});  
                  return;  
                }  
                
                reader.onload = function (e) {  
                  var img = new Image();  
                  img.onload = function () {  
                        // 不要超出最大宽度  
                        var w = Math.min(maxWidth, img.width);  
                        // 高度按比例计算  
                        var h = img.height * (w / img.width);  
                        var canvas = document.createElement('canvas');  
                        var ctx = canvas.getContext('2d');  
                        // 设置 canvas 的宽度和高度  
                        canvas.width = w;  
                        canvas.height = h;  
                        ctx.drawImage(img, 0, 0, w, h);  
                        var base64 = canvas.toDataURL('image/png');  
                        
                        // 插入到预览区  
                        var $preview = $('<li class="weui_uploader_file weui_uploader_status" style="background-image:url(' + base64 + ')"><div class="weui_uploader_status_content">0%</div></li>');  
                        $('.weui_uploader_files').append($preview);  
                        var num = $('.weui_uploader_file').length;  
                        $('.js_counter').text(num + '/' + maxCount);  
                        
                        // 然后假装在上传，可以post base64格式，也可以构造blob对象上传，也可以用微信JSSDK上传  
                        
                        var progress = 0;  
                        function uploading() {  
                          $preview.find('.weui_uploader_status_content').text(++progress + '%');  
                          if (progress < 100) {  
                            setTimeout(uploading, 10);  
                          }  
                          else {  
                                // 如果是失败，塞一个失败图标  
                                //$preview.find('.weui_uploader_status_content').html('<i class="weui_icon_warn"></i>');  
                                $preview.removeClass('weui_uploader_status').find('.weui_uploader_status_content').remove();  
                              }  
                            }  
                            setTimeout(uploading, 30);  
                          };  
                          
                          img.src = e.target.result;  
                        };  
                        reader.readAsDataURL(file);  
                      }  
                    });
    	
					var $uploaderFiles=$(".weui_uploader_files");
					var $gallery = $("#gallery");
					var $galleryImg = $("#galleryImg");
			        $uploaderFiles.on("click", "li", function(){
			            $galleryImg.attr("style", this.getAttribute("style"));
			            $gallery.show();
			            $(this).addClass("chooseUpload");
			        });
			        $gallery.on("click", function(){
			            $gallery.hide();
			        });
			        $(".weui-icon-delete").on('click',function() {
			            $(".chooseUpload").remove();
			            var num = $('.weui_uploader_file').length;
	                     $('.js_counter').text(num + '/' + maxCount);
			   })
    })
	
	
